Executives at Philadelphia's local CBS station rejoiced when Access Hollywood presenter Larry Mendte returned from Los Angeles to present the news. Paired with 36-year-old Alycia Lane, 51-year-old Mendte made an immediate impression, boosting the station's ratings.

But behind the squeaky-clean onscreen chemistry, a feud festered between the two news anchors. Lane allegedly told her co-host during an on-set row that she was "the rising star" and he was on the way out. Her salary raced past his to $780,000.

So Mendte snooped on her email more than 500 times, sending material intended to discredit her to local gossip columns. This week, Mendte was sentenced to six months' house arrest by a Philadelphia court, ordered to carry out 150 hours of community service and fined $5,000 (£3,300). The station sacked Mendte in June when the allegations surfaced.

"I felt I was in trouble," Mendte told the court. "My career, my future, my family's future was in trouble. And, this is where I got into more trouble - federal trouble."

Prosecutors painted a portrait of a man obsessed by insecurities and the possibility that a colleague might outshine him.

"Mendte checked Ms Lane's email from home, from the station, from the Union League and from his vacation home," prosecutor Michael Levy told the court. "When he got up in the morning; before he went to bed; while waiting for the commercials to finish when he was on the air."

In court Mendte said: "I'm grateful Alycia is here so I can apologise personally. I am sorry for what I did. I am sorry you did not think my [public] apology was sincere. It was and I am sincere now."

One email he leaked told of a run-in Lane had with New York police resulting in her arrest. Charges were dropped, but not before CBS3 in Philadelphia had fired Lane. She is suing the station for wrongful dismissal. Lane did not speak at the trial, but her lawyer, Paul Rosen, told reporters: "I don't think she will ever accept that apology until her life is restored from what he did to her. What he did was methodical, intentional and he took every chance he could to try to have her face incarceration for a crime she didn't commit."